Semi-automatic string trimmer head

Abstract

A string trimmer providing an incremental indexing of line when the head is stopped and started. The preferred embodiment of the string trimmer head includes a spool member within the body member, the spool member being coaxially positioned within the body member and being rotatable therewith. The spool member includes a grooved end face with a cam channel having at least one switchback and one arcuate segment. A connecting means attached to the body member includes a connector which runs within the cam channel. Upon starting the rotation, the connector runs along an arcuate segment of the cam channel (permitting relative rotation between the spool member and the body member thereby indexing a length of line) until contacting a switchback stopping point. The connector is biased to move along the switchback and resets along the switchback upon stopping of rotation.

What is claimed is: 
     
       1. A feed head for a string trimmer or the like, said feed head being rotationally drivable at a high speed about a center axis thereof and comprising: a hollow housing structure circumscribing said center axis and having a side wall portion with a line exit port therein;   a spool member coaxially disposed within said housing structure for driven rotation therewith about said center axis, said spool member being adapted to hold a length of flexible cutting line with a free end portion of the line extending outwardly through said exit port to be whirled at high speed, in a cutting plane transverse to said center axis, in response to driven rotation of said feed head; and   cooperating means on said housing structure and said spool member for creating a predetermined incremental relative rotation between said housing structure and said spool member about said center axis, in a manner correspondingly lengthening the free end portion of the line, in response to a driven rotational acceleration of said feed head about said center axis from a stopped condition.   
     
     
       2. The feed head of claim 1 wherein: said cooperating means include groove means formed in one of said housing structure and said spool member, and pin means carried by the other of said housing structure and said spool member, said pin means being received in said groove means for guided movement along their length.   
     
     
       3. A feed head for a string trimmer or the like comprising: a housing structure rotatable at high speed about a center axis thereof and having a generally radially facing side wall portion with a line exit port formed therethrough;   line storage means, carried within said housing structure for rotation therewith, for storing within said housing structure a length of flexible cutting line having a free end portion extending outwardly through said line exit port to be whirled at high speed, in a cutting plane transverse to said center axis, during operative high speed rotation of said housing structure about said center axis; and   line advancement means for automatically lengthening the free end portion of the cutting line, by a predetermined length increment, in response to rotational acceleration of said housing structure from a stopped condition thereof.   
     
     
       4. For use in conjunction with a string trimmer feed head or the like rotatable at high speed about a center axis thereof to whirl, in a cutting plane transverse to said center axis, an outwardly projecting free end portion of a quantity of flexible cutting line stored within the feed head, a method of periodically lengthening the free line end to compensate for shortening thereof during operation of the feed head, said method comprising the steps of: sensing a rotational acceleration of the feed head from a stopped condition thereof; and   automatically causing a predetermined length of the stored line quantity to be paid out, to thereby add a corresponding length increment to the free line end portion, in response to the sensed rotational acceleration of the feed head from a stopped condition thereof.